Some place to learn UI , how to make beautiful apps

http://inspired-ui.com/

http://inspirationmobile.tumblr.com/

http://www.pttrns.com/

http://www.pinterest.com/efreedman/ux-mobile-design-inspiration/

 UX  basic: http://www.uxapprentice.com/

UX advantage: http://uxmastery.com/

"We challenged ourselves to create a visual language for our users that synthesizes the classic principles of good design with the innovation and possibility of technology and science. This is material design. This spec is a living document that will be updated as we continue to develop the tenets and specifics of material design."

GoalsCreate a visual language that synthesizes classic principles of good design with the innovation and possibility of technology and science.Develop a single underlying system that allows for a unified experience across platforms and device sizes. Mobile precepts are fundamental, but touch, voice, mouse, and keyboard are all first-class input methods.

http://www.google.com/design/spec/material-design/introduction.html#